Synthesis And Application Of Functional Modifier On Silk Fibroin Based On The Mannich Reaction

Silk has the characteristics of gorgeous appearance,elegant luster,soft hand-feel and health care,and has been widely used in textile materials since antiquity.In recent years,it has been applied to biomaterial base materials because of its good biocompatibility and degradability.However,as a protein material,silk has storage stability problems such as photoinduced yellowing,brittleness,and wrinkles.It is necessary to use some functional modification methods to improve its performance.Based on the Mannich reaction modification principle,six dye-type modifiers containing primary amine structures were prepared.The effects of amino acid type,position and water solubility on the modification efficiency of the Mannich reaction were investigated by using dyes with color and easy quantitative analysis.From the relative fixation rate and density function theory(DFT)analysis,it can be concluded that the modifier has a higher efficiency for the Mannich reaction of silk if the modifier has an aromatic primary amine structure,good water solubility and a small amino steric hindrance.The result of structure-activity relationship lays a theoretical foundation for the design and synthesis of other functional modifiers for silk proteins.According to the above research results,a water-soluble aromatic primary amine ultraviolet absorber(S-H-1)and a hindered amine light stabilizer(S-H-2)were designed and synthesized,and their molecular structures were characterized by FT-IR,MS and ~1H-NMR.The UV-visible absorption spectrum indicates that both of the light stabilizers have ultraviolet absorption properties and have no absorption in the visible light region.The silk was modified by the Mannich reaction,and the results showed that the modified silk had better fastness to washing;and at the same dosage,the S-H-1 modified silk showed higher UPF than that of the commercial UVA UV-FAST-W.After silk modification of S-H-1 and S-H-2,there was no significant effect on silk whiteness;The silk was modified with 2%owf S-H-1 and S-H-2.After10 h UV irradiation,the breaking strength of S-H-1 and S-H-2 modified silk increased by 8.2%and 8.5%,respectively,compared with the original silk;And the average yellowing rate of S-H-1 and S-H-2 modified silk are 28.13%and 47.09%of the original silk.Therefore,the S-H-1 modification has better anti-yellowing properties,S-H-1 and S-H-2 can improve the light stability of silk.Two aromatic primary FWAs of P-1 and P-2 were designed and synthesized,and their molecular structures were characterized by FT-IR,MS and ~1H-NMR.It was found by UV-visible absorption spectrum and fluorescence emission spectroscopy that the two fluorescent whitening agents have the property of absorbing ultraviolet rays and emitting fluorescence.The fluorescent whitening agents P-1 and P-2 were used to modify the silk by the Mannich reaction.The effect of the amount of fluorescent whitening agent on the whiteness of silk was investigated.The reflectivity of the silk before and after the modification was compared.The results showed that P-1 and P-2modification made the silk whiteness increase from 66.42 to 71.61 and 73.70respectively.The results of this thesis indicate that the structure of aromatic primary amine,water-soluble and para-amino group is more favorable for the Mannich reaction-modified silk;the designed light stabilizer and FWAs are modified by the Mannich reaction to obtain better modification effect.This provides a useful reference for the further design of the Mannich reaction-based silk protein functionalizing modifier.